The present invention generally relates to constructions for intravascular treatment devices useful for removing vascular occlusion material from a vascular occlusion or from a vascular lumen. The invention more specifically relates to xe2x80x9cexpandablexe2x80x9d intravascular occlusion material removal devices, as well as to methods of using those devices to treat vascular diseases. In this context, xe2x80x9cexpandablexe2x80x9d means that the burr can ablate a lumen having a larger diameter than the diameter of the lumen of the guide catheter to which the burr is advanced.
Vascular diseases, such as atherosclerosis and the like, have become quite prevalent in the modem day. These diseases may present themselves in a number of forms. Each form of vascular disease may require a different method of treatment to reduce or cure the harmful effects of the disease. Vascular diseases, for example, may take the form of deposits or growths in a patient""s vasculature which may restrict, in the case of a partial occlusion, or stop, in the case of a total occlusion, blood flow to a certain portion of the patient""s body. This can be particularly serious if, for example, such an occlusion occurs in a portion of the vasculature that supplies vital organs with blood or other necessary fluids.
To treat these diseases, a number of different therapies are being developed. While a number of invasive therapies are available, it is desirable to develop non-invasive therapies as well. Minimally invasive therapies may be less risky than invasive ones, and may be more welcomed by the patient because of the possibility of decreased chances of infection, reduced post-operative pain, and less post-operative rehabilitation. One type of non-invasive therapy for vascular diseases is pharmaceutical in nature. Clot-busting drugs have been employed to help break up blood clots which may be blocking a particular vascular lumen. Other drug therapies are also available. Further, minimally invasive intravascular treatments exist that are not only pharmaceutical, but also revascularize blood vessels or lumens by mechanical means. Two examples of such intravascular therapies are balloon angioplasty and atherectomy which physically revascularize a portion of a patient""s vasculature.
Balloon angioplasty comprises a procedure wherein a balloon catheter is inserted intravascularly into a patient through a relatively small puncture, which may be located proximate the groin, and intravascularly navigated by a treating physician to the occluded vascular site. The balloon catheter includes a balloon or dilating member which is placed adjacent the vascular occlusion and then is inflated. Intravascular inflation of the dilating member by sufficient pressures, on the order of 5 to 12 atmospheres or so, causes the balloon to displace the occluding matter to revascularize the occluded lumen and thereby restore substantially normal blood flow through the revascularized portion of the vasculature. It is to be noted, however, that this procedure does not remove the occluding matter from the patient""s vasculature, but displaces it.
While balloon angioplasty is quite successful in substantially revascularizing many vascular lumens by reforming the occluding material, other occlusions may be difficult to treat with angioplasty. Specifically, some intravascular occlusions may be composed of an irregular, loose or heavily calcified material which may extend relatively far along a vessel or may extend adjacent a side branching vessel, and thus are not prone or susceptible to angioplastic treatment. Even if angioplasty is successful, thereby revascularizing the vessel and substantially restoring normal blood flow therethrough, there is a chance that the occlusion may recur. Recurrence of an occlusion may require repeated or alternative treatments given at the same intravascular site.
Accordingly, attempts have been made to develop other alternative mechanical methods of minimally invasive, intravascular treatment in an effort to provide another way of revascularizing an occluded vessel and of restoring blood flow through the relevant vasculature. These alternative treatments may have particular utility with certain vascular occlusions, or may provide added benefits to a patient when combined with balloon angioplasty and/or drug therapies.
One such alternative mechanical treatment method involves removal, not displacement, as is the case with balloon angioplasty, of the material occluding a vascular lumen. Such treatment devices, sometimes referred to as atherectomy devices, use a variety of means, such as lasers, and rotating cutters or ablaters, for example, to remove the occluding material. The rotating cutters may be particularly useful in removing certain vascular occlusions. Since vascular occlusions may have different compositions and morphology or shape, a given removal or cutting element may not be suitable for removal of a certain occlusion.
Alternatively, if a patient has multiple occlusions in his vasculature, a given removal element may be suitable for removing only one of the occlusions. Suitability of a particular cutting element may be determined by, for example, its size or shape. Thus, a treating physician may have to use a plurality of different treatment devices to provide the patient with complete treatment. This type of procedure can be quite expensive because multiple pieces of equipment may need to be used (such intravascular devices are not reusable because they are inserted directly into the blood stream), and may be tedious to perform because multiple pieces of equipment must be navigated through an often-tortuous vascular path to the treatment site.
The present invention pertains generally to devices for performing atherectomy. In particular, various embodiments of an atherectomy device are disclosed which can ablate a lumen having a larger diameter than the diameter of the lumen of the guide catheter through which the device is advanced.
In one embodiment, an elongate shaft is provided having a proximal and a distal end. The shaft defines a lumen. A burr deflector is disposed at the distal end of the shaft. The burr deflector includes a burr engaging surface. An elongate rotatable drive shaft extends through the lumen of the first shaft. The drive shaft has a proximal end and a distal end. A burr is disposed at the distal end of the drive shaft. The drive shaft and burr are shiftable relative to the burr deflector. The drive shaft and burr may be shifted between a first position and a second position, wherein the burr is transversely shifted relative to the burr deflector. Preferably, the deflection is co-linear to the length of the drive shaft.
The burr engaging surface is preferably disposed at an acute angle to the length of the first shaft. The burr preferably includes an engaging surface disposed at an acute angle relative to the drive shaft such that the engaging surfaces provide a path along which the burr can shift transversely relative to the burr deflector.
In yet another embodiment of a device in accordance with the present invention an elongate shaft is provided which has a proximal and a distal end. The shaft defines a lumen. An elongate rotatable drive shaft extends through the lumen. The drive shaft has a proximal end and a distal end. A burr is disposed at the distal end of the drive shaft. A bushing is disposed around the drive shaft proximate the burr. A steering line is connected to the bushing. The steering line can be pulled by an operator to shift the bushing and thus the burr and drive transversely.
In yet another embodiment of a device in accordance with the present invention, an elongate rotatable drive shaft is provided having a proximal and a distal end. An ablation burr is disposed at the distal end of the drive shaft. The ablation burr includes a mechanism which expands transversely in response to the centrifugal force generated when the burr rotates.
In one embodiment, the mechanism is generally tubular and has a proximal end and a distal end constrained against expansion. The central portion of the tubular member is allowed to expand under the influence of the centrifugal force. In yet another embodiment of the mechanism, a member having a generally helical cross-section is provided which tends to unwind, increasing its transverse diameter as the burr rotates. In yet another embodiment of the mechanism, a line is provided having a proximal end and a distal end. The ends of the line are held a distance apart less than the length of the line. An abrasive is disposed on the line. As the burr is rotated, the line moves transversely. In yet another embodiment of the mechanism includes a plurality of bristles which can shift transversely under the influence of centrifugal force.
In another embodiment of the atherectomy device in accordance with the present invention, an elongate rotatable drive shaft is provided having a proximal end and a distal end. A lumen is defined through the elongate drive shaft. A balloon including an outer surface and defining a balloon enclosure in fluid communication with the inflation lumen is disposed at the distal end of the drive shaft. An abrasive is disposed on the outer surface of the balloon. The balloon can be dilated by pressure or centrifugal force to increase the transverse dimension of the abrasive surface.
In yet another embodiment of an atherectomy device in accordance with the present invention, an elongate shaft is provided having a proximal end and a distal end. The shaft defines a drive shaft lumen and an inflation lumen. A rotatable drive shaft, having a proximal end and a distal end, is disposed in the drive shaft lumen. An ablating burr is disposed at the distal end of the drive shaft. A balloon is disposed eccentrically on the drive shaft proximate the burr. The balloon can be inflated to push against the vessel wall and shift the drive shaft and burr transversely within the vessel lumen.
In yet another embodiment of an atherectomy device in accordance with the present invention, an elongate rotatable drive shaft is provided having a proximal end and a distal end. An ablation burr is eccentrically connected to the drive shaft at the distal end of the shaft. A counterweight is disposed on the burr to place the center of mass of the burr in line with the longitudinal axis of the drive shaft. The presence of the counterweight dampens whipping of the burr which might otherwise occur during rotation of the drive shaft. This embodiment is related to that disclosed in U.S. patent application Ser. No. 08/987,969, filed Dec. 10, 1997 and entitled ASYMMETRIC BURRS FOR ROTATIONAL ABLATION incorporated herein by reference.
In yet another embodiment of the atherectomy device in accordance with the present invention, an elongate shaft is provided having a proximal end and a distal end. The shaft defines a lumen therethrough. A rotatable drive shaft having a proximal end and a distal end, is disposed through the lumen. A burr, including a plurality of spring members is disposed at the distal end of the drive. The drive shaft and the burr are shiftable between a first position and a second position. In the first position, the spring members are disposed at least in part within the lumen of the first shaft and are transversely constrained thereby. In the second position, the spring members are transversely restrained less than in the first position such that the burr has a greater transverse dimension in the second position than in the first position.
In yet another embodiment of an atherectomy device in accordance with the present invention, an elongate rotatable drive shaft is provided having a proximal end and a distal end, the drive shaft includes a generally helical-shaped portion proximate the distal end biased to expand when unconstrained. An abrasive is disposed on the helical portion. The helical portion can be advanced to the site where atherectomy will be performed in a constrained and collapsed state through a guide catheter. When the helical shaped portion exits the guide catheter, the helically shaped portion, then unconstrained, will expand transversely.